The preferred embodiments of the present invention generally relate to an electrical connector assembly having a receptacle connector mateable with a header connector, in a small envelope and with high signal performance characteristics.
It is common, in the electronics industry, to use right angled connectors for electrical connection between two printed circuit boards or between a printed circuit board and conducting wires. The right angled connector typically has a large plurality of pin receiving terminals and, at right angles thereto, pins (for example compliant pins) that make electrical contact with a printed circuit board. Post headers on another printed circuit board or a post header connector can thus be plugged into the pin receiving terminals making electrical contact there between. The transmission frequency of electrical signals through these connectors is very high and requires not only balanced impedance of the various contacts within the terminal modules to reduce signal lag and reflection but also shielding between rows of terminals to reduce crosstalk.
Impedance matching of terminal contacts has already been discussed in U.S. Pat. Nos. 5,066,236 and 5,496,183. Right angle connectors have also been discussed in these patents, whereby the modular design makes it easy to produce shorter or longer connectors without redesigning and tooling up for a whole new connector but only producing a new housing part into which a plurality of identical terminal modules are assembled. As shown in the ""236 patent, shielding members can be interposed between adjacent terminal modules. An insert may be used to replace the shield or a thicker terminal module may be used to take up the interposed shielding gap if the shielding is not required. The shield disclosed in the ""236 patent is relatively expensive to manufacture and assemble. The shielded module disclosed in the ""183 patent includes a plate-like shield secured to the module and having a spring arm in the plate section for electrically engaging an intermediate portion of a contact substantially encapsulated in a dielectric material. The shield arrangement of the ""183 patent, however, requires sufficient space between adjacent through-holes of the board to avoid inadvertent short circuits. Furthermore, both the insulated module and the shield must be modified if the ground contact is to be relocated in the connector.
An alternative electrical connector assembly has been proposed in U.S. Pat. No. 5,664,968, in which each terminal module has a plurality of contacts including a mating contact portion, a connector connecting portion and an intermediate portion there between with some or all of the intermediate portions encapsulated in an insulated web. Each of the modules has an electrically conductive shield mounted thereto. Each shield includes at least a first resilient arm in electrical engagement with a selected one of the contacts in the module to which the shield is mounted and at least a second resilient arm extending outwardly from the module and adapted for electrical engagement with another selected contact in an adjacent terminal module of the connector assembly.
Conventional connector assemblies, such as in the ""236, ""183 and ""968 patents, are typically designed for use both in single ended applications as well as in differential pair applications. In single ended applications, the entire signal is directed in a first direction along one conductor and then the entire signal is subsequently returned in the opposite direction along a different conductor. Each conductor is connected to a contact within a connector assembly, and thus the entire signal is directed in a first direction through one pin or contact and in the opposite direction through a separate pin or contact. In differential applications, the signal is divided and transmitted in the first direction over a pair of conductors (and hence through a pair of contacts or pins). The return signal is similarly divided and transmitted in the opposite direction over the same pair of conductors (and hence through the same pair of pins or contacts).
The differences in the signal propagation path of single ended versus differential pair applications cause differences in the signal characteristics. Signal characteristics may include impedance, propagation delay, noise, skew, and the like. The signal characteristics are also effected by the circuitry used to transmit and receive the signals. The circuitry involved in transmitting and receiving signals entirely differs for single ended and differential. applications. The differences in the transmit and receive circuitry and the signal propagation paths yield different electrical characteristics, such as for impedance, propagation delay, skew and noise. The signal characteristics are improved or deteriorated by varying the structure and configuration of the connector assembly. The structure and configuration for connector assemblies optimized for single ended applications differ from connector assemblies optimized for use in differential pair applications.
Heretofore, it has been deemed preferable to offer a common connector assembly useful in both single ended and differential pair applications. Consequently, the connector assembly is not optimized for either applications. A need remains for a connector assembly optimized for differential pair applications.
Moreover, most connector assemblies must meet specific space constraints depending upon the type of application in which the connector assembly is used while maintaining high signal performance. By way of example only, certain computer specifications, such as for the Compact PCI specification, define the dimensions for an envelope in which the connector assembly must fit, namely an HM-type connector which represents an industry standard connector. However, the HM connector does not necessarily offer adequate signal performance characteristics desirable in all applications. Instead, in certain applications, higher signal characteristics may be preferable, such as offered by the HS3 connector offered by Tyco Electronics Corp.
However, certain conventional connectors that offer higher signal characteristics may not satisfy the envelope dimensions of an HM type connector standard. For example, an HM connector is designed to be mounted on the edge of a printed circuit board to connect the printed circuit board at a right angle to a daughter card. The HM connector includes a mating face that straddles the edge of the printed circuit board. The side of the HM connector is L shaped and affords a mating face located both above and below the printed circuit board surface. The contacts on an HM connector are staggered to straddle the edge of the printed circuit board. Certain types of connectors that offer high signal characteristics include contacts only along one side of the board, not staggered on either side of a printed circuit board.
By way of example only, certain conventional connectors, such as the HS3 connectors, include ground shields and signal contact terminals. The ground shields are located in the header connector and engage ground contacts in the receptacle connector when the header and receptacle connectors are Joined. When mating the header and receptacle, it is preferable that the ground contact and ground shields engage one another before signal contacts in the header and receptacle engage one another.
However, in conventional connector assemblies, in order for tips of the ground contacts to engage the tips of the ground shields first, they should be longer than the signal contacts. The ground contacts and shields touch, when the header and receptacle are only partially mated. As the header and receptacle are further joined to the fully mated position, the point of connection between the tip of the ground contact and the ground shield moves from the tip of the ground shield toward the base of the ground shield. When fully mated, the tip of the ground contact is in electrical contact with the ground shield at a point proximate the base of the ground shield.
The signal performance is inferior for connector assemblies, in which the ground contact electrically engages the ground shield only proximate the base of the ground shield since the outer portion of the ground shield functions as a stub antenna to transmit electromagnetic (EM) interference. The EM interference caused by the ground shield interferes with the signal characteristics of the connector assembly.
Further, controlling the impedance within a connector assembly typically enhances the electrical performance of the connector assembly. In general, as the walls of the cavities of the receptacle housing are located closer to the contact the impedance is decreased. Therefore, it is preferable that the cavity walls be located close to the contact. The contours of the cavity walls of conventional connector assemblies, however, do not correspond with the contour of the contact. Instead, conventional connector housings define a cavity bounded by relatively straight walls. Therefore, the interior cavities of current receptacle housings are approximately cube-shaped. The contact is generally inserted through one end of the cube Consequently, if a non-cube, non-square, or non-rectangular shaped contact is utilized, the interior surfaces of the cavity walls do not follow the contours of the contact. Because the contours of the cavity walls do not correspond to the contours of the contact, a relatively large amount of air surrounds the contact within the cavity. The relatively large amount of air surrounding the contact produces impedance. That is, impedance increases as more air surrounds the contact which, in turn, reduces signal performance.
A need remains for an improved connector assembly capable of satisfying small envelope dimensions, while affording high quality signal performance characteristics.
At least one preferred embodiment of the present invention provides an electrical connector assembly having a receptacle connector mateable with a header connector in a small envelope while affording high quality signal performance. The assembly includes an insulated housing and a plurality of terminal modules mounted to the insulated housing. Each terminal module has an insulated molded body enclosing multiple connector contacts having opposed mating portions. Each terminal module includes contacts formed into at least one differential pair.
In accordance with at least one alternative embodiment, a terminal module is provided that is mountable to an insulated housing of an electrical connector. The terminal module includes receptacle contacts and leads connected thereto for carrying signals through the terminal module. The terminal module also includes a differential shell having an open-sided chamber formed therein. The differential shell includes walls defining-chambers that receive the receptacle contacts. Each chamber may have open front and open rear ends and have at least one open side. Each of the chambers accepts a corresponding receptacle contact through the open side thereof. The walls of the differential shells have non-linear contours along the interior surfaces that substantially conform to a contour of the receptacle contacts received therein.
In accordance with at least one alternative embodiment, each differential shell is provided with a floor, sidewalls and a center wall. At least one of the floor, sidewalls and center wall include a non-linear, curved surface following a contour of a corresponding surface of an associated receptacle contact. The differential shells may include an open top sidewall. The chamber may include interior surfaces forming a curved contour that closely follows and substantially conforms to exterior surfaces of the receptacle contacts. The receptacle contacts may be formed in a fork shape with a flared base and fingers located closer to one another than to the flared base. The walls of the differential shell may substantially conform to outer surfaces of the fingers.
In accordance with at least one alternative embodiment, a terminal module is provided that is mountable to an insulated housing of an electrical connector, in which the terminal module includes a differential shell and receptacle contacts. The differential shell includes an open-sided cavity therein. The receptacle contacts have exterior surfaces that, when received in the open-sided cavity, conform to interior surfaces thereof. The differential shell includes side walls defining the open-sided cavity that have projections formed on interior surfaces thereof to cooperate with the sidewalls to substantially conform to a contour of the receptacle contacts.
In accordance with at least one alternative embodiment, the terminal module includes a lead frame that includes leads arranged in at least two differential pairs of leads. Each lead includes board contacts and receptacle contacts at opposite ends thereof. The receptacle contacts and the board contacts are interconnected through intermediate conductive portions of the leads. Optionally, the lead frame may include four differential pairs of conductive leads, with each conductive lead having board contacts and receptacle contacts at opposite ends thereof. The receptacle contacts and board contacts may be interconnected through intermediate conductive portions.
Optionally, the one sided cavity of the terminal module may include a floor, sidewalls, a center wall, flared portions and ramp blocks that define a contour of the open-sided cavity.
The receptacle contacts may be inserted into the differential shell through an open side thereof to enhance electrical performance by enabling the receptacle contacts to be closely spaced to inner surfaces of the open-sided cavity. The receptacle contacts may be located at a terminal end of a lead that passes through an open rear end of an associated differential shell.
In accordance with at least one alternative embodiment, an electrical connector assembly is provided having a receptacle connector mateable with a header connector operable in at least differential pair applications. The electrical connector assembly includes an insulated housing and a plurality of terminal modules mounted to the insulated housing. Each terminal module may include an insulated body enclosing multiple signal conductors with signal contacts on opposed ends thereof. The signal conductors and contacts may be formed in differential pairs. The terminal module also further includes a plurality of open-sided differential shells formed within the terminal module and receptacle contacts that conform to an inner cavity within the differential shell. Each differential shell includes walls with non-linear interior surfaces that define an open-sided cavity conforming to a contour of the receptacle contacts. The differential shells receive the receptacle contacts through the open side of the cavity.
In accordance with yet a further alternative embodiment, the insulated housing includes insulated walls that close the open-sided differential shells when the terminal modules are inserted into the insulated housing. Optionally, the insulated housing may include a plurality of support posts that cooperate to define a plurality of slots. Each slot receives one of the terminal modules. The support posts are spaced apart from one another to form, along each row of support posts, a series of gaps therebetween. The insulated housing includes thin insulating walls filling the gaps between the support posts. Optionally, a plurality of ground terminals may be located within each terminal module immediately adjacent an open side of each differential shell. The insulated housing may arrange the insulated walls to be accepted between the ground terminals and the open sides of the differential shells to form an insulative layer between the ground terminals and the receptacle contacts.